The objective of this competitive renewal application is to define the biochemical events that mediate the effects of tyrosine protein kinases on cell growth and metabolism. The proposed studies will focus on a tyrosine kinase signaling paradigm that lead to the activation of pp90 rsk (Rsk) in Xenopus oocytes and eggs. Previous work funded by this grant have led to the identification of the MAP kinase/Rsk pathway in Xenopus oocytes. In the current application, the investigator proposes to build on these findings in order to explore the mechanisms by which this pathway exerts control on oocyte maturation. The project has three specific aims. Aim 1 proposes to purify, clone, and characterize protein kinases that phosphorylate and activate Rsk. Aim 2 proposes to investigate the mechanism of activation of Rsk by multi-site phosphorylation mediated by multiple kinases. Aim 3 proposes to determine the mechanisms of inhibition of MAP kinase activation by cAMP.